1. Field of the Invention
The invention relates to a method for producing an anti-friction bearing comprising a carrier metal, which forms a back bearing side, and a bearing metal, wherein the carrier metal is made from a bronze-based alloy, and an anti-friction bearing comprising a carrier metal, which forms a back bearing side, and a bearing metal, wherein the carrier metal is made from a bronze-based alloy.
2. Description of the Related Art
On the one hand future engines will require higher strengths for bearing shells, i.e. for the bearing metal. On the other hand however they also need to have suitably effective tribological properties which are provided in part by additional coatings, good damping properties and sufficient adaptability of the complete bearing system to the shaft or the bearing pin. Known multi-layered anti-friction bearings address these various problems by having different layer systems, for example a steel back as a carrier layer and a bearing metal layer applied on top, for example with an aluminium base, and possibly a running layer applied over this. In the prior art the property profile of an anti-friction bearing is determined and defined by the selection of the individual layers.
However, for particular applications, in particular in order to control fretting problems more effectively, a back bearing layer with a non-ferrous metal base is required. The back metal layer is in direct contact with the bearing mount after the installation of the anti-friction bearing half shell. In this case owing to cyclical, unwanted relative movements of the components to one another at very low amplitude on the contact surfaces between the bearing and bearing mount, particularly with highly loaded connecting rod bearings, frictional welding or friction corrosion may occur, i.e. localised damage, and thereby the “seizure” of the anti-friction bearing in the bearing housing. This damage mechanism is referred to generally as fretting.
It is known to use bronze alloys for the back metal layer instead of steel. For example, AT 502 546 A1 describes a back metal layer made from copper alloys, such as brass or bronze.
It is also known from the prior to make bearing metal layers out of bronze. For example DE 20 53 696 A describes an anti-friction bearing consisting of at least two layers made of metal materials, one layer of which is configured as a running layer facing the bearing pin, whereby the running layer is configured as a hard layer of low thickness and is underlaid by a layer or a material of much lower hardness. Said material can be a lead bronze, a tin bronze, a lead-tin-bronze, an aluminium alloy or pure aluminium.
The bronze alloy needs to be of high strength when in use as a back metal layer, in order to ensure that it fits well into the bearing mount. Furthermore, this high strength has a negative effect in single layer bearings, i.e. anti-friction bearings, in which the back metal layer also forms the running layer or bearing metal layer, on the damping properties and the adaptability of the anti-friction bearing.
DE 15 27 549 B describes a semi-finished product for producing anti-friction bearing shells with an evenly formed thin running layer in the form of plates cut from double-layered or multi-layered composite material which are shaped into semi-cylindrical bearing shells by exerting pressure on the joint faces, wherein the composite material to be worked into bearing shells with varying average strengths over its width, averaged over the material thickness, is configured so that at points at which thickened areas are to be expected during the shaping of the composite material by compression there are increased average strengths. The composite material can be subjected to treatment by heat and/or rolling to make areas of varying strength.
In this way a semi-finished product is made available for producing anti-friction bearing shells, in which the thickened areas occurring during the shaping of the anti-friction bearing shells are avoided from the start on the carrier layers that are the basis of the strength of the bearing. In this way with simple composite bearings the running layer to be applied prior to the shaping of the bearing, for example a white metal layer, can be made thinner to increase the permanent impact strength of the bearing. The invention is intended to make it possible with triple-material bearings to apply the later running layer of the bearing prior to its shaping, in order in this way to avoid the necessity of galvanic application and its associated increased production costs and restriction to galvanically applicable alloys. The intermediate layer in the anti-friction bearings described in this patent can be made of bronze. Thus according to this document it is also necessary to have a multi-layered structure for the anti-friction bearing.